As depicted in FIGS. 1 and 2, the human heart 30 is contained in the mediastinum 32 within a conical sac of serous membrane called the pericardium 34. There are generally two layers to pericardium 34; the fibrous pericardium 35 and the serous pericardium 36. The fibrous pericardium 35 is a superficial layer comprising dense connective tissue and it encloses serous pericardium 36. The serous pericardium 36 itself has two layers. The layer adjacent the fibrous pericardium is the parietal layer 37 and the layer next to the heart is the visceral layer 38, also known as the epicardium. Between the parietal 37 and visceral 38 layers exists a small cavity known as the pericardial space 39. This pericardial space may be void or partially filled with a lubricious fluid 39a. 
Pacing of the heart is usually achieved by pacing leads introduced transvenously. In some cases, however, the chamber of the heart or a specific location on the chamber of the heart is not accessible using a transvenous approach and must be placed surgically.
Leads placed on the surface of the heart, such as in contact with the visceral pericardium, require a method of fixation to keep them in place. In the prior art, pacing the epicardium is usually accomplished via a screw in lead placed surgically.
To pace the epicardium, a pacing lead is positioned with one or more electrodes in contact with the visceral pericardium. For effective pacing, electrodes on the pacing lead must be in constant electrical conductive contact with the surface of the visceral pericardium. Conductivity is most preferably sufficient so as to enable a pacing voltage of 3 volts or less, although for various reasons, prior art leads often develop much higher pacing thresholds.
To accomplish constant contact, different pacing lead configurations have been previously used to assist in the placement and retention of the pacing lead in the desired position. These prior leads, however, all have certain drawbacks making them not entirely satisfactory. For example they require placement through the parietal pericardium either surgically or percutaneously. They are usually screwed into place and frequently develop high thresholds. Other leads have been developed which employ a helical structure oriented along the longitudinal axis of the lead. The helical structure exerts a lateral biasing force against the walls of the space to assist in fixation of the lead. These prior helical leads, however, are sometimes difficult to stabilize and may be prone to “overturn” or rotate about the longitudinal axis of the lead when in place, thereby interrupting electrical contact of the electrodes.
The present inventor has recognized that prior art leads and fixation methods that do not employ screws or suture are not entirely suitable for placement in the pericardial space through the pericardium (surgical or percutaneously). Further, the present inventor recognizes that prior art leads, fixation and stabilization methods are not entirely suitable for leads introduced into the pericardial space through the venous system. Hence, there is still a need for a lead and passive fixation method assuring stable pacing from the epicardial surface whether introduced transvenously through the coronary venous microcirculation or through the wall of a chamber of the heart or through the fibrous pericardium. Because the general problems discussed above have not been addressed by conventional pacing leads, there is a current need for pacing leads addressing the problems and deficiencies inherent with the prior designs.